iio:dac:dpot-dac: Swap of.h for mod_devicetable.h

This driver never used anything in the of specific header.
It just wants the struct of_device_id from mod_devicetable.h.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Peter Rosin <peda@axentia.se>

drivers/iio/dac/dpot-dac.c

@@ -30,7 +30,7 @@
 #include <linux/iio/consumer.h>
 #include <linux/iio/iio.h>
 #include <linux/module.h>
-#include <linux/of.h>
+#include <linux/mod_devicetable.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>